In the field of infrared (IR) imaging, the current objective is to provide large area focal plane arrays at low cost with high performance. InSb, HgCdTe, and quantum well infra-red photodetector (QWIP) technologies have demonstrated high performance large area focal plane arrays. Each of these technologies has various strengths and weaknesses. InSb photodetectors offer high performance and ease of fabrication, but must be cooled to approximately 80 K. HgCdTe photodetectors can be designed to operate in the middle wavelength IR (MWIR) corresponding to a wavelength range of 3 to 5 μm, the long wavelength IR (LWIR) corresponding to a wavelength range of 8 to 12 μm, or the very long wavelength IR (VLWIR) corresponding to a wavelength range of greater than 12 μm. However, HgCdTe photodetectors require very tight tolerances in material and fabrication uniformity to ensure high performance. QWIP photodetectors have been demonstrated in the MWIR, the LWIR, and the VLWIR while requiring only moderate tolerances in both material and fabrication uniformity.
Because photodetectors fabricated from HgCdTe have the greatest potential performance at a given operating temperature, significant time and effort have been expended to improve the HgCdTe starting material and fabrication process. While progress has been made, the cost of implementing these improvements is significant. Thus, there exists a need for a design that places fewer and/or less stringent requirements upon the starting material and/or the fabrication process.